William Henry Harrison gave a LONG inaugural speech, in the cold, without a jacket. Big mistake.

Turns out that wasn't his cause of death. Yes, he gave a long speech (the longest speech in history--two hours), in the cold rain, after riding on horseback (also in the rain). He was over 80 years old.

But he didn't get sick for another three weeks. His illness lasted just nine days, and then he died. Turns out that the White House water supply was exposed to what they called "night soil," which is their euphemism for human waste in a cistern. Historians now think he died from Typhoid, the result of his immune system weakened by age. See wiki for more.